Multilayer Polypropylene Films and Methods of Making and Using Same

ABSTRACT

A method including forming a bilayer polymer film having an oriented polypropylene film and a metallocene-catalyzed polypropylene film wherein the metallocene-catalyzed polypropylene film has a seal initiation temperature of from 80° C. to 130° C. A laminate including a biaxially oriented polypropylene film, a metallocene-catalyzed polypropylene film, and a substrate, wherein the metallocene-catalyzed polypropylene film is disposed between the biaxially oriented polypropylene film and the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable

BACKGROUND

1. Technical Field

This disclosure relates to methods of preparing polypropylene films.More specifically, this disclosure relates to multi-layer polypropylenefilms for use in thermo-lamination applications and methods of makingand using same.

2. Background

Synthetic polymeric materials, particularly polypropylene resins, aremanufactured into a variety of end-use articles ranging from medicaldevices to materials packaging. Many industries, such as the packagingindustry, utilize these polypropylene materials in various manufacturingprocesses to create a variety of finished goods including containers,packaging films for food packaging, thermo-lamination films for bookcovers, etc. For example, producing thermo-lamination films may involveextruding a layer of ethylene vinyl acetate (EVA) onto a plastic film(e.g., polypropylene) to form a bilayer film. Next, the EVA side of thebilayer film may be thermo-laminated to different types of substrates(e.g., paper, wood, etc.) to form polypropylene-EVA laminates.

One challenge to the utility of polypropylene-EVA laminates is achievingsufficient bond strength between the polypropylene film and the EVAlayer. In order to improve the bonding between these layers, a tie layermay be placed between the polypropylene film and the EVA layer. However,adding a tie layer increases the cost associated with producing suchmaterials and may detrimentally affect one of more physical properties(e.g., low haze, high gloss) of the material. Thus an ongoing needexists for novel laminate compositions having desirable physical and/ormechanical properties.

SUMMARY

Disclosed herein is a method including forming a bilayer polymer filmhaving an oriented polypropylene film and a metallocene-catalyzedpolypropylene film wherein the metallocene-catalyzed polypropylene filmhas a seal initiation temperature of from 80° C. to 130° C. The bilayerpolymer film may have of an oriented polypropylene film and ametallocene-catalyzed polypropylene film. The metallocene-catalyzedpolypropylene film may have a thickness of from 0.1 mil to 20 mil. Theoriented polypropylene film may include uniaxially orientedpolypropylene film, biaxially oriented polypropylene film, orcombinations thereof. The oriented polypropylene film may be coronatreated. The oriented polypropylene film may have a thickness of from0.1 mil to 20 mil. The bilayer polymer film may have an adhesivestrength of from 0.1 lbf to 10 lbf. The bilayer polymer film may have agloss 45° of from 60 to 99. The bilayer polymer film may have a hazepercentage of from 0.5% to 10%. The bilayer polymer film may have athickness of from 0.2 mil to 20 mil. The forming of the bilayer polymerfilm may occur at a temperature of from 420° F. to 530° F. The formingof the bilayer polymer film may occur by extrusion coating themetallocene-catalyzed polypropylene film onto the biaxially orientedpolypropylene film. The method may further include thermolaminating thebilayer polymer film with a substrate to form a laminate wherein themetallocene-catalyzed polypropylene film is disposed between thebiaxially oriented polypropylene film and the substrate. The substratemay include paper, plastic, metal, wood, fabric, glass or combinationsthereof. The laminate may be substantially free ofethylene-vinyl-acetate. The oriented polypropylene film may be subjectedto a surface modification process. An article as produced by any of thepreviously disclosed methods.

Also disclosed herein is a laminate including a biaxially orientedpolypropylene film, a metallocene-catalyzed polypropylene film, and asubstrate wherein the metallocene-catalyzed polypropylene film isdisposed between the biaxially oriented polypropylene film and thesubstrate. The metallocene-catalyzed polypropylene film may have a sealinitiation temperature of from 80° C. to 130° C. The laminate may besubstantially free of ethylene-vinyl-acetate.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and theadvantages thereof, reference is now made to the following briefdescription, taken in connection with the accompanying drawings anddetailed description, wherein like reference numerals represent likeparts.

FIG. 1 is a schematic diagram of an extrusion coating apparatus.

FIGS. 2A and 2B illustrate a 180° peel force test.

FIG. 3 is a plot of force as a function of extension for the 180° peeltest results for Sample 1 from Example 1.

FIG. 4 is a plot of force as a function of extension for the 180° peeltest results for Sample 2 from Example 2.

FIG. 5 is a plot of force as a function of extension for the 180° peeltest results for Sample 3 from Example 3.

FIG. 6 is a plot of force as a function of extension for the 180° peeltest results for Sample 4 from Example 4.

FIG. 7 is a plot of average force as a function of extension for the180° peel test results for Samples 1-4 from Examples 1-4.

FIGS. 8-11 are plots of force as a function of extension for the 180°peel test results for Samples 9-12 from Example 7.

FIG. 12 is a plot of average force as a function of extension for the180° peel test results for Samples 9-12 from Example 7.

FIG. 13 is a plot of average force as a function of extension for the180° peel test results for Sample 2, 11, and 12 from Examples 2 and 7.

DETAILED DESCRIPTION

It should be understood at the outset that although an illustrativeimplementation of one or more embodiments are provided below, thedisclosed systems and/or methods may be implemented using any number oftechniques, whether currently known or in existence. The disclosureshould in no way be limited to the illustrative implementations,drawings, and techniques illustrated below, including the exemplarydesigns and implementations illustrated and described herein, but may bemodified within the scope of the appended claims along with their fullscope of equivalents.

As used herein oriented polypropylene is designated “oPP;”metallocene-catalyzed polypropylene is designated “mPP;” bilayer polymerfilm is designated “BPF;” biaxially oriented polypropylene is designate“BOPP;” high crystallinity polypropylene is designated “HCPP;”polypropylene heterophasic copolymers are designated “PPHC;” ethylenepropylene rubber is designated “EPR;” melt flow rate is designated“MFR;” metallocene-catalyzed random ethylene propylene copolymer isdesignated “mREPC;” seal initiation temperature is designated “SIT;”percentage xylene solubles is designated “XS %;” and ethylene vinylacetate is designated “EVA.”

Disclosed herein are multilayer polymer films and methods of making andusing same. The multilayer polymer films include at least one orientedpolypropylene (oPP) film layer and at least one metallocene-catalyzedpolypropylene (mPP) film layer. In an embodiment, the multilayer filmincludes greater than 2 layers, alternatively 3, 4, 5, or 6 layers.Alternatively, the multilayer film includes 2 layers. Hereinafter, forsimplicity, the discussion will refer to bilayer polymer films althoughit is to be understood that polymer films having greater than two layersare also contemplated.

In an embodiment, a bilayer polymer film (BPF) may have an orientedpolypropylene (oPP) film layer and a metallocene-catalyzed polypropylene(mPP) film layer.

In an embodiment, the BPF includes an oriented polypropylene film layer.The polypropylene may be a homopolymer, a high crystallinitypolypropylene, a polypropylene heterophasic copolymer, or combinations(e.g., blends) thereof. The polypropylene may be formed into a film andoriented to produce an oriented polypropylene film layer as described inmore detail herein.

The polypropylene may be a homopolymer provided however that thehomopolymer may contain up to 5% of another alpha-olefin, including butnot limited to C₂-C₈ alpha-olefins such as ethylene and 1-butene.Despite the potential presence of small amounts of other alpha-olefins,the polypropylene is generally referred to as a polypropylenehomopolymer (or substantially a homopolymer). Polypropylene homopolymerssuitable for use in this disclosure may include any type ofpolypropylene known in the art with the aid of this disclosure. Forexample, the polypropylene homopolymer may be, isotactic polypropylene,hemi-isotactic, or combinations thereof. A polymer is “isotactic” whenall of its pendant groups are arranged on the same side of the chain. Inhemi-isotactic polymer, every other repeat unit has a randomsubstituent.

A polypropylene suitable for use in this disclosure may be characterizedby a number average molecular weight Mn of from 3.3×10⁴ Daltons to8.3×10⁴ Daltons, alternatively from 4.1×10⁴ Daltons to 7.5×10⁴ Daltons,alternatively from 5.0×10⁴ Daltons to 6.6×10⁴ Daltons; a weight averagemolecular weight of from 3.0×10⁵ Daltons to 6.2×10⁵ Daltons,alternatively from 3.5×10⁵ Daltons to 5.7×10⁵ Daltons, alternativelyfrom 4.0×10⁵ Daltons to 5.1×10⁵ Daltons; a polydispersity index of from4.9 to 11.0, alternatively from 6.0 to 10.0, alternatively from 7.0 to9.0; and a z-average molecular weight of from 9.7×10⁵ Daltons to 3.2×10⁶Daltons, alternatively from 1.3×10⁶ Daltons to 2.8×10⁶ Daltons,alternatively from 1.7×10⁶ Daltons to 2.5×10⁶ Daltons. Specifically, fora polymeric composition the number-average molecular weight M_(n) isgiven by equation 1:

M_(n)=ΣN_(x)M_(x)  (1)

where N_(x) is the mole-fraction (or the number-fraction) of moleculeswhose weight is M_(x) The weight-average molecular weight M_(w) is givenby equation 2:

M_(w)=Σw_(x)M_(x)  (2)

where w_(x) is the weight-fraction of molecules whose weight is M_(x).The polydispersity index (PDI) is given by equation 3:

PDI=M _(W) /M _(n)  (3)

The z-average molecular weight (M_(z)) is given by equation 4:

M _(z) =Σw _(x) M _(x) ² /Σw _(x) M _(x)  (4)

where w_(x) is the weight-fraction of molecules whose weight is M.

In an embodiment, a polypropylene suitable for use in this disclosuremay have a density of from 0.895 g/cc to 0.920 g/cc, alternatively from0.900 g/cc to 0.915 g/cc, and alternatively from 0.905 g/cc to 0.915g/cc as determined in accordance with ASTM D1505; a melting temperatureof from 150° C. to 170° C., alternatively from 155° C. to 168° C., andalternatively from 160° C. to 165° C. as determined by differentialscanning calorimetry; a melt flow rate of from 0.5 g/10 min. to 30 g/10min., alternatively from 1.0 g/10 min. to 15 g/10 min., andalternatively from 1.5 g/10 min. to 5.0 g/10 min. as determined inaccordance with ASTM D1238 condition “L”; a tensile modulus of from200,000 psi to 350,000 psi; alternatively from 220,000 psi to 320,000psi, and alternatively from 250,000 psi to 320,000 psi as determined inaccordance with ASTM D638; a tensile stress at yield of from 3,000 psito 6,000 psi, alternatively from 3,500 psi to 5,500 psi, andalternatively from 4,000 psi to 5,500 psi as determined in accordancewith ASTM D638; a tensile strain at yield of from 5% to 30%,alternatively from 5% to 20%, and alternatively from 5% to 15% asdetermined in accordance with ASTM D638; a flexural modulus of from120,000 psi to 330,000 psi, alternatively from 190,000 psi to 310,000psi, and alternatively of from 220,000 psi to 300,000 psi as determinedin accordance with ASTM D790; a Gardner impact of from 3 in-lb to 50in-lb, alternatively from 5 in-lb to 30 in-lb, and alternatively from 9in-lb to 25 in-lb as determined in accordance with ASTM D2463; a NotchedIzod Impact Strength of from 0.2 ft lb/in to 20 ft lb/in, alternativelyfrom 0.5 ft lb/in to 15 ft lb/in, and alternatively from 0.5 ft lb/in to10 ft lb/in as determined in accordance with ASTM D256A; a hardnessshore D of from 30 to 90, alternatively from 50 to 85, and alternativelyfrom 60 to 80 as determined in accordance with ASTM D2240; and a heatdistortion temperature of from 50° C. to 125° C., alternatively from 80°C. to 115° C., and alternatively from 90° C. to 110° C. as determined inaccordance with ASTM D648.

Examples of polypropylene homopolymers suitable for use in thisdisclosure include without limitation grades 3371, 3271, 3270, 3276, and3377, which are polypropylene homopolymers commercially available fromTotal Petrochemicals USA, Inc. In an embodiment, the polypropylenehomopolymer (e.g., grade 3377) has generally the physical properties setforth in Table 1.

TABLE 1 Properties Typical Value Test Method Resin properties Density,g/cc 0.905 ASTM D1505 Melt Flow Rate (MFR), g/10 min. 3.5 ASTM D1238condition “L” Melting Point, ° F. 325 DSC Film Properties, OrientedHaze, % 1 ASTM D1003 Gloss 45° 90 ASTM D 2457 Ultimate tensile MD, psi19,000 ASTM D 882 Ultimate tensile TD, psi 38,000 ASTM D 882 Tensilemodulus, MD, psi 350,000 ASTM D 882 Tensile modulus, TD, psi 600,000ASTM D 882 Elongation MD, % 130 ASTM D 882 Elongation TD, % 50 ASTM D882 WVTR, g/100 in 2/24 h/mil 0.3 ASTM F-1249-90 at 100° F., 90% RH

In another embodiment, the polypropylene may be a high crystallinitypolypropylene homopolymer (HCPP). The HCPP may contain primarilyisotactic polypropylene. The isotacticity in polymers may be measuredvia ¹³C NMR spectroscopy using meso pentads and can be expressed aspercentage of meso pentads (% mmmm). As used herein, the term “mesopentads” refers to successive methyl groups located on the same side ofthe polymer chain. In an embodiment, the HCPP has a meso pentadspercentage of greater than 97%, or greater than 98%, or greater than99%. The HCPP may have some amount of atactic or amorphous polymer. Theatactic portion of the polymer is soluble in xylene, and is thus termedthe xylene soluble fraction (XS %). In determining XS %, the polymer isdissolved in boiling xylene and then the solution cooled to 0° C. thatresults in the precipitation of the isotactic or crystalline portion ofthe polymer. The XS % is that portion of the original amount thatremained soluble in the cold xylene. Consequently, the XS % in thepolymer is indicative of the extent of crystalline polymer formed. Thetotal amount of polymer (100%) is the sum of the xylene soluble fractionand the xylene insoluble fraction, as determined in accordance with ASTMD5492-98. In an embodiment, the HCPP has a xylene soluble fraction ofless than 1.5%, or less than 1.0%, or less than 0.5%.

In an embodiment, an HCPP suitable for use in this disclosure may have adensity of from 0.895 g/cc to 0.920 g/cc, alternatively from 0.900 g/ccto 0.915 g/cc, and alternatively from 0.905 g/cc to 0.915 g/cc asdetermined in accordance with ASTM D1505; a melt flow rate of from 0.5g/10 min. to 30 g/10 min., alternatively from 1.0 g/10 min. to 15 g/10min., and alternatively from 1.5 g/10 min. to 5.0 g/10 min. asdetermined in accordance with ASTM D1238; a secant modulus in themachine direction (MD) of from 350,000 psi to 420,000 psi; alternativelyfrom 380,000 psi to 420,000 psi, and alternatively from 400,000 psi to420,000 psi as determined in accordance with ASTM D882; a secant modulusin the transverse direction (TD) of from 400,000 psi to 700,000 psi,alternatively from 500,000 psi to 700,000 psi, and alternatively from600,000 psi to 700,000 psi as determined in accordance with ASTM D882; atensile strength at break in the MD of from 19,000 psi to 28,000 psi,alternatively from 22,000 psi to 28,000 psi, and alternatively from25,000 psi to 28,000 psi as determined in accordance with ASTM D882; atensile strength at break in the TD of from 20,000 psi to 40,000 psi,alternatively from 30,000 psi to 40,000 psi, and alternatively of from35,000 psi to 40,000 psi as determined in accordance with ASTM D882; anelongation at break in the MD from 50% to 200%, alternatively from 100%to 180%, and alternatively from 120% to 150% as determined in accordancewith ASTM D882; an elongation at break in the TD of from 50% to 150%,alternatively from 60% to 100%, and alternatively from 80% to 100% asdetermined in accordance with ASTM D882; a melting temperature of from150° C. to 170° C., alternatively from 155° C. to 170° C., andalternatively from 160° C. to 170° C. as determined by differentialscanning calorimetry; a gloss at 45° of from 70 to 95, alternativelyfrom 75 to 90, and alternatively from 80 to 90 as determined inaccordance with ASTM D2457; a percentage haze of from 0.5% to 2.0%,alternatively from 0.5% to 1.5%, and alternatively from 0.5% to 1.0% asdetermined in accordance with ASTM D1003; and a water vapor transmissionrate of from 0.15 to 0.30 g-mil/100 in²/day, alternatively from 0.15 to0.25 g-mil/100 in²/day, and alternatively from 0.20 to 0.21 g-mil/100in²/day as determined in accordance with ASTM F1249-90.

An example of an HCPP suitable for use in this disclosure includeswithout limitation grade 3270, which is an HCPP commercially availablefrom Total Petrochemicals USA, Inc. The HCPP (e.g., grade 3270) maygenerally have the physical properties set forth in Table 2.

TABLE 2 Properties Typical Value Test Method Physical Density, g/cc0.910 ASTM D1505 Melt Mass-Flow Rate (MFR) 2.0 ASTM D1238 (230° C./2.16kg), g/10 min. BOPP Mechanical Secant Modulus MD, psi 420,000 ASTM 882Secant Modulus TD, psi 700,000 ASTM 882 Tensile Strength at Break MD,psi 28,000 ASTM 882 Tensile Strength at Break TD, psi 39,000 ASTM 882Elongation at Break MD, % 150 ASTM 882 Elongation at Break TD, % 60 ASTM882 Thermal Melting Temperature, ° F. 329 DSC Optical Gloss (45°) 85ASTM D2457 Haze, % 1.0 ASTM D1003 Barrier Water Vapor Transmission, 0.2ASTM F1249- 100° F., 90% R.H, g-mil/100 in²/day 90

In another embodiment, the polypropylene may be a polypropyleneheterophasic copolymer (PPHC) wherein a polypropylene homopolymer phaseor component is joined to a copolymer phase or component. The PPHC mayhave from greater than 6.5% to less than 11.5% by weight ethylene,alternatively from 8.5% to less than 10.5%, alternatively from 9.5%ethylene based on the total weight of the PPHC. Herein, percentages of acomponent refer to the percent by weight of that component in the totalcomposition unless otherwise noted.

The copolymer phase of a PPHC may be a random copolymer of propylene andethylene, also referred to as an ethylene/propylene rubber (EPR). PPimpact copolymers show distinct homopolymer phases that are interruptedby short sequences or blocks having a random arrangement of ethylene andpropylene. In comparison to random copolymers, the block segmentscomprising the EPR may have certain polymeric characteristics (e.g.,intrinsic viscosity) that differ from that of the copolymer as a whole.In an embodiment, the EPR portion of the PPHC includes greater than 14wt. % of the PPHC, alternatively greater than 18 wt. % of the PPHC,alternatively from 14 wt. % to 18 wt. % of the PPHC.

The amount of ethylene present in the EPR portion of the PPHC may befrom 38 wt. % to 50 wt. %, alternatively from 40 wt. % to 45 wt,% basedon the total weight of the EPR portion. The amount of ethylene presentin the EPR portion of the PPHC may be determined spectrophotometricallyusing a Fourier transform infrared spectroscopy (FTIR) method.Specifically, the FTIR spectrum of a polymeric sample is recorded for aseries of samples having a known EPR ethylene content. The ratio oftransmittance at 720 cm⁻¹/900 cm⁻¹ is calculated for each ethyleneconcentration and a calibration curve may then be constructed. Linearregression analysis on the calibration curve can then be carried out toderive an equation that is then used to determine the EPR ethylenecontent for a sample material.

The EPR portion of the PPHC may exhibit an intrinsic viscosity differentfrom that of the propylene homopolymer component. Herein intrinsicviscosity refers to the capability of a polymer in solution to increasethe viscosity of said solution. Viscosity is defined herein as theresistance to flow due to internal friction. In an embodiment, theintrinsic viscosity of the EPR portion of the PPHC may be greater than2.0 dl/g, alternatively from 2.0 dl/g to 3.0 dl/g, alternatively from2.4 dl/g to 3.0 dl/g, alternatively from 2.4 dl/g to 2.7 dl/g,alternatively from 2.6 dl/g to 2.8 dl/g. The intrinsic viscosity of theEPR portion of the PPHC is determined in accordance with ASTM D5225.

In an embodiment, the PPHC may have a melt flow rate (MFR) of from 65g/10 min. to 130 g/10 min., alternatively from 70 g/10 min. to 120 g/10min., alternatively from 70 g/10 min. to 100 g/10 min., alternativelyfrom 70 g/10 min. to 90 g/10 min., alternatively from 75 g/10 min. to 85g/10 min., alternatively 90 g/10 min. Excellent flow properties asindicated by a high MFR allow for high throughput manufacturing ofmolded polymeric components. In an embodiment, the PPHC is a reactorgrade resin without modification, which may also be termed a low orderPP. In some embodiments, the PPHC is a controlled rheology grade resin,wherein the melt flow rate has been adjusted by various techniques suchas visbreaking. For example, MFR may be increased by visbreaking asdescribed in U.S. Pat. No. 6,503,990, which is incorporated by referencein its entirety. As described in that publication, quantities ofperoxide are mixed with polymer resin in flake, powder, or pellet formto increase the MFR of the resin. MFR as defined herein refers to thequantity of a melted polymer resin that will flow through an orifice ata specified temperature and under a specified load. The MFR may bedetermined using a dead-weight piston Plastometer that extrudespolypropylene through an orifice of specified dimensions at atemperature of 230° C. and a load of 2.16 kg in accordance with ASTMD1238.

Representative examples of suitable PPHCs include without limitationgrades 4920W and 4920WZ, which are impact copolymer resins commerciallyavailable from Total Petrochemicals USA Inc. In an embodiment, the PPHC(e.g., grade 4920W) has generally the physical properties set forth inTable 3.

TABLE 3 Properties Typical Value ASTM Method Physical Melt Flow, g/10min. 100 D1238 Density, g/cc 0.905 D1505 Melting Point, ° C. 160-165 DSCMechanical Tensile strength at Yield, psi (MPa) 3700 (25) D638Elongation at Yield, % 6 D638 Flexural Modulus, psi (MPa) 190,000(1,300) D790 Notched-ft. lb./in. (J/m)  1.0 (50) ASTM D256A Thermal HeatDeflection, ° C. 90 D648

In an embodiment, the polypropylene may also contain additives to impartdesired physical properties, such as printability, increased gloss, or areduced blocking tendency. Examples of additives include withoutlimitation stabilizers, ultra-violet screening agents, oxidants,anti-oxidants, anti-static agents, ultraviolet light absorbents, fireretardants, processing oils, mold release agents, coloring agents,pigments/dyes, fillers, and/or other additives known to one skilled inthe art. The aforementioned additives may be used either singularly orin combination to form various formulations of the polymer. For example,stabilizers or stabilization agents may be employed to help protect thepolymer resin from degradation due to exposure to excessive temperaturesand/or ultraviolet light. These additives may be included in amountseffective to impart the desired properties. Effective additive amountsand processes for inclusion of these additives to polymeric compositionsmay be determined by one skilled in the art with the aid of thisdisclosure.

The polypropylene for oPP film may be prepared using any suitablecatalyst known to one or ordinary skill in the art. For example, thepolypropylene may be prepared using a Ziegler-Natta catalyst.

In an embodiment, the polypropylene is prepared using Ziegler-Nattacatalysts, which are typically based on titanium and organometallicaluminum compounds, for example triethylaluminum (C₂H₅)₃A1.Ziegler-Natta catalysts and processes for forming such catalysts areknown in the art and examples of such are described in U.S. Pat. Nos.4,298,718; 4,544,717; and 4,767,735, each of which is incorporated byreference herein.

The polypropylene may be formed by placing propylene alone in a suitablereaction vessel in the presence of a catalyst (e.g., Ziegler-Natta) andunder suitable reaction conditions for polymerization thereof. Standardequipment and processes for polymerizing the propylene into a polymerare known to one skilled in the art. Such processes may include solutionphase, gas phase, slurry phase, bulk phase, high pressure processes orcombinations thereof. Such processes are described in detail in U.S.Pat. Nos. 5,525,678; 6,420,580; 6,380,328; 6,359,072; 6,346,586;6,340,730; 6,339,134; 6,300,436; 6,274,684; 6,271,323; 6,248,845;6,245,868; 6,245,705; 6,242,545; 6,211,105; 6,207,606; 6,180,735; and6,147,173, which are incorporated herein by reference in their entirety.

In an embodiment, the polypropylene is formed by a gas phasepolymerization process. One example of a gas phase polymerizationprocess includes a continuous cycle system, wherein a cycling gas stream(otherwise known as a recycle stream or fluidizing medium) is heated ina reactor by heat of polymerization. The heat is removed from thecycling gas stream in another part of the cycle by a cooling systemexternal to the reactor. The cycling gas stream containing one or moremonomers may be continuously cycled through a fluidized bed in thepresence of a catalyst under reactive conditions. The cycling gas streamis generally withdrawn from the fluidized bed and recycled back into thereactor. Simultaneously, polymer product may be withdrawn from thereactor and fresh monomer may be added to replace the polymerizedmonomer. The reactor pressure in a gas phase process may vary from about100 psig to about 500 psig, or from about 200 psig to about 400 psig, orfrom about 250 psig to about 350 psig. The reactor temperature in a gasphase process may vary from about 30° C. to about 120° C., or from about60° C. to about 115° C., or from about 70° C. to about 110° C., or fromabout 70° C. to about 95° C., for example U.S. Pat. Nos. 4,543,399;4,588,790; 5,028,670; 5,317,036; 5,352,749; 5,405,922; 5,436,304;5,456,471; 5,462,999; 5,616,661; 5,627,242; 5,665,818; 5,677,375; and5,668,228, which are incorporated herein by reference in their entirety.

In an embodiment, the polypropylene is formed by a slurry phasepolymerization process. Slurry phase processes generally include forminga suspension of solid, particulate polymer in a liquid polymerizationmedium, to which monomers and optionally hydrogen, along with catalyst,are added. The suspension (which may include diluents) may beintermittently or continuously removed from the reactor where thevolatile components can be separated from the polymer and recycled,optionally after a distillation, to the reactor. The liquefied diluentemployed in the polymerization medium may include a C₃ to C₇ alkane(e.g., hexane or isobutene). The medium employed is generally liquidunder the conditions of polymerization and relatively inert. A bulkphase process is similar to that of a slurry process. However, a processmay be a bulk process, a slurry process or a bulk slurry process.

In an embodiment, the BPF includes metallocene-catalyzed polypropylene(mPP) film layer (i.e., a film layer comprising polypropylene producedusing a metallocene catalyst). The mPP may be a homopolymer or acopolymer, for example a copolymer of propylene with one or more alphaolefin monomers such as ethylene, butene, hexene, etc. In an embodiment,the mPP film includes a metallocene-catalyzed random ethylene-propylene(C₂/C₃) copolymer (mREPC) and may include of from 2 wt. % to 10 wt. %ethylene, alternatively from 3 wt. % to 9 wt. % ethylene, alternativelyfrom 4 wt. % to 8 wt. % ethylene. The mPP film layer may have a sealinitiation temperature (SIT) of from 80° C. to 130° C., alternativelyfrom 95° C. to 125° C., alternatively from 90° C. to 120° C. Herein theSIT refers to the minimum sealing temperature required to form a seal ofsignificant strength, which varies depending on the applications.Further, a mPP suitable for use in this disclosure may be characterizedby a number average molecular weight Mn of from 5.1×10⁴ to 9.3×10⁴,alternatively from 5.8×10⁴ to 8.6×10⁴, alternatively from 6.5×10⁴ to7.9×10⁴; a weight average molecular weight of from 1.67×10⁵ to 2.20×10⁵,alternatively from 1.75×10⁵ to 2.11×10⁵, alternatively from 1.84×10⁵ to2.02×10⁵; a polydispersity index of from 2.1 to 3.3, alternatively from2.3 to 3.1, alternatively from 2.5 to 2.9; and a z-average molecularweight of from 2.98×10⁵ to 4.22×10⁵, alternatively from 3.19×10⁵ to4.01×10⁵, alternatively from 3.40×10⁵ to 3.81×10⁵.

In ethylene-propylene random copolymers, the ethylene molecules areinserted randomly into the polymer backbone between repeating propylenemolecules, hence the term random copolymer. In the preparation of amREPC a certain amount of amorphous polymer is produced. This amorphousor atactic polymer is soluble in xylene and is thus termed the xylenesoluble fraction or percent xylene solubles (XS %). In determining XS %,the polymer is dissolved in hot xylene and then the solution is cooledto 0° C. which results in the precipitation of the isotactic orcrystalline portion of the polymer. The XS % is that portion of theoriginal amount that remained soluble in the cold xylene. Consequently,the XS % in the polymer is further indicative of the extent ofcrystalline polymer formed. In an embodiment, the mREPC has a xylenesoluble fraction of from 0.1% to 6.0%; alternatively from 0.2% to 2.0%;and alternatively from 0.3% to 1.0%, as determined in accordance withASTM D 5492-98.

In an embodiment, an mREPC suitable for use in this disclosure may havea density of from 0.890 g/cc to 0.920 g/cc, alternatively from 0.895g/cc to 0.915 g/cc, and alternatively from 0.900 g/cc to 0.910 g/cc asdetermined in accordance with ASTM D-1505. In an embodiment, an mREPCsuitable for use in this disclosure may have a melt flow rate of from0.5 g/10 min. to 2000 g/10 min., alternatively from 1 g/10 min. to 1000g/10 min., and alternatively from 10 g/10 min. to 500 g/10 min., asdetermined in accordance with ASTM D-1238 condition “L.” In anembodiment, a film prepared from an mREPC suitable for use in thisdisclosure may have a gloss at 45° of from 70 to 95, alternatively from75 to 90, and alternatively from 80 to 90 as determined in accordancewith ASTM D-2457.

An example of a suitable mREPC suitable for use in this disclosureincludes without limitation a metallocene catalyzed ethylene-propylenerandom copolymer known as grade EOD 02-15 available from TotalPetrochemicals USA, Inc. In an embodiment, the mREPC (e.g., grade EOD02-15) generally has the physical properties set forth in Table 4.

TABLE 4 Resin Properties Typical Value ASTM Method Melt Flow, g/10 min.11 D 1238 Density, g/cc 0.895 D 1505 Melting Point, ° F. (° C.)   246(119) DSC ⁽¹⁾ Film Properties ⁽¹⁾ Non-oriented- 2 mil (50 μm) Haze, %0.3 D 1003 Gloss @ 45°, % 90 D 2457 1% Secant Modulus (MD), psi (MPa)50,000 (345) D 882 Ultimate Tensile Strength (MD), 5,000 (35) D 882 psi(MPa) Ultimate Elongation (MD), % 700 D 882 Heat Seal Temperature ⁽²⁾, °F. (° C.)   221 (105) ⁽¹⁾ MP determined with a DSC-2 DifferentialScanning Calorimeter. ⁽²⁾ Seal condition: die pressure 60 psi (413 kPa),dwell time 1.0 sec

mPP homopolymers may be formed by placing propylene in a suitablereaction vessel in the presence of a metallocene catalyst and/oroptionally additives and under suitable reaction conditions forpolymerization thereof.

mPP copolymers (i.e., mREPC) may be formed by placing propylene incombination with a co-monomer (e.g., ethylene) in a suitable reactionvessel in the presence of a metallocene catalyst and/or optionallyadditives and under suitable reaction conditions for polymerizationthereof. Preparation of mPPs (i.e., mREPCs) are described in furtherdetail in U.S. Pat. Nos. 5,158,920, 5,416,228, 5,789,502, 5,807,800,5,968,864, 6,225,251, and 6,432,860, each of which is incorporatedherein by reference in its entirety.

In an embodiment, a method of preparing a BPF includes preparing an oPPfilm and contacting an mPP film with the oPP film to form a multi-layerfilm (e.g., a bilayer film). In such an embodiment, the oPP film may beprepared by first melting the polypropylene in an extruder. Next, themolten polypropylene is extruded through a slot or a die to form a thinextruded polypropylene film. The extruded polypropylene film is thenadhered to a cooled surface, such as a chill roll that may be in contactwith a water bath. The chill roll functions to immediately quench thefilm. The polypropylene film may then be passed through rollers designedto stretch the film in one direction to produce a uniaxially orientedpolypropylene film, alternatively in differing axial directions toproduce biaxially oriented polypropylene (i.e., BOPP) films. Theuniaxially or biaxially oriented film (collectively referred to hereinas oPP film) may be further trimmed and rolled for transport or storage.In an embodiment, the oPP film has a thickness of from 0.1 mil to 20mil, alternatively from 0.25 mil to 20 mil, alternatively from 0.30 milto 20 mil.

In some embodiments, the oPP film may be subjected to a surfacemodification process designed to increase the surface tension of thefilm. Examples of surface modification processes include withoutlimitation corona treatment, flame treatment and plasma treatment.Corona treatment is an electrical process that uses ionized air toincrease the surface tension of nonporous substrates. Flame treatment isa process of burning away surface contaminants by forcibly spraying aflame onto a substrate. Plasma treatment is a process of creating plasmain an inert gas to increase surface energy and wetting ability of asubstrate. In an embodiment, the oPP film of this disclosure issubjected to corona treatment following extrusion. Methods andconditions for corona treatment of an oPP film are known to one ofordinary skill in the art with the aid of this disclosure.

Examples of suitable oPP films include without limitation TAPEFILM TH20and TAPEFILM TH30 which are oPP tape films commercially available fromOppFilm Fallsington, Pa. In an embodiment, the oPP films (e.g., TAPEFILMTH20, TAPEFILM TH30) have generally the physical properties set forth inTable 5.

TABLE 5 Typical Value Properties TAPEFILM TH20 TAPEFILM TH30 ASTM MethodHaze, % 1.0 D 1003 Gloss at 45° 90 D 2457 Dynamic C.O.F (Film/film) 03 D1894 Tensile strength MD, N/mm² 150 D 882 Tensile strength TD, N/mm² 300D 882 Elongation at break MD, % 130 D 882 Elongation at break TD, % 50 D882 Modulus MD, N/mm² 2000 D 882 Modulus TD, N/mm² 2800 D 882 Wettension (corona treatment), dinas, cm 38 2578 Water vapor transmission38°, 90% HR 5.6 4.7 F 1249 Oxygen transmission at 22° C., 0% HR 18001600 D 1434

After the oPP film is prepared, the method of preparing a BPF mayfurther include extrusion coating an mPP layer onto the oPP film layer.FIG. 1 is a schematic diagram of an extrusion coating apparatus 100 foruse in the process of preparing a BPF. Referring to FIG. 1, the processmay be carried out by providing an oPP, which is usually in the form ofa rolled oPP film 110. The rolled oPP film 110 is unwound using anunwinder 105 where an unrolled oPP film 115 is guided using guiderollers 120 and 125 toward a nip roller 130. Next, an mPP 140 is meltedand extruded through a die 135 at a temperature of from 420° F. to 530°F., alternatively from 440° F. to 520° F., alternatively from 490° F. to510° F. The extruded mPP 140 is then laid onto (i.e., contacted with)the unrolled oPP film 115 at a nip 150. Contacting of the mPP 140 andthe oPP film 110 at nip 150 at adequate pressure causes the mPP 140 toadhere to the oPP film 115 to form a BPF 155. In an embodiment, theapparatus is configured such that the pressure applied may be adjustedto meet a process-desired need. The BPF 155 is then passed onto acooling cylinder such as a chilled roll 145, and guided with guideroller 160 towards rollers 165. From rollers 165, the BPF 155 is woundusing winder 170 and collected as a rolled BPF film 175.

The oPP film layer may have a thickness of from 0.1 mil to 20 mil,alternatively from 0.25 mil to 20 mil, alternatively from 0.3 mil to 20mil. The mPP film layer may have a thickness of from 0.1 mil to 20 mil,alternatively from 0.25 mil to 20 mil, alternatively from 0.3 mil to 20mil. In such embodiments, the resultant BPF having an oPP film layer anda mPP film layer has a thickness of from 0.2 mil to 20 mil,alternatively from 0.25 mil to 20 mil, alternatively from 0.3 mil to 20mil.

In an embodiment, a BPF of the type described herein may include an oPP,an mPP and a tie layer. Alternatively the BPF does not include a tielayer. Tie layers are adhesive layers that are typically added toimprove the adhesion between two materials.

The BPF comprising an mPP film layer and an oPP film layer of the typedescribed herein may have display a number of desirable physical and/oroptical properties. In an embodiment, the BPFs of the type describedherein have a haze percentage of from 0.5% to 10%, or from 1% to 9%, orfrom 1.5% to 7%. Haze is the cloudy appearance of a material caused bylight scattered from within the material or from its surface. The hazeof a material can be determined in accordance with ASTM D1003-00 for ahaze percentage of equal to or lower than 30%. A material having a hazepercentage of greater than 30% can be determined in accordance with ASTME167.

In an embodiment, BPFs of the type described herein may have a gloss 45°of from 60 to 99, or from 61 to 98, or from 62 to 95. The gloss of amaterial is based on the interaction of light with the surface of amaterial, more specifically the ability of the surface to reflect lightin a specular direction. Gloss is measured by measuring the degree ofgloss as a function of the angle of the incident light, for example at45° incident angle (also known as “gloss 45°”), and may be determined inaccordance with ASTM D2457.

In an embodiment, a BPF of the type described herein may be used inthermo-lamination applications to form laminates. In such an embodiment,the BPF may be applied to a substrate, wherein the mPP film layer isdisposed between the oPP film layer and the substrate, and then heatedto form a laminate. The substrate may include any suitable substratesuch as paper, plastic, metal, wood, fabric, glass, or combinationsthereof. In thermo-lamination applications, the mPP film layer of theBPF may function as a heat seal layer.

In an embodiment, a laminate is formed which has a substrate, an mPPfilm layer and an oPP film layer of the type described herein. In anembodiment, the laminate includes less than 1 wt. % EVA, alternativelyless than 0.5, 0.1, 0.01, 0.001 or 0.001 wt. % EVA. Alternatively, thelaminate is substantially free of EVA.

The laminate including a BPF having an mPP film layer and an oPP filmlayer of the type described herein may display desirable mechanicalproperties. In an embodiment, the laminate may exhibit an adhesivestrength of from 0.1 lb_(f) to 10 lb_(f) alternatively from 0.25 lb_(f)to 9 lb_(f), alternatively from 0.5 lb_(f) to 7 lb_(f) based on a 180°peel strength test.

FIGS. 2A and 2B illustrate a 180° peel strength test 200. Referring toFIG. 2A, the test 200 is carried out by contacting a BPF 205 comprisingan oPP film layer 210 and an mPP film layer 215 with a substrate such asa bond paper 220 wherein the mPP film layer 215 of the BPF 205 is facingthe bond paper 220. Next, two heated bars 225 are pressed (arrows 230)onto the BPF 205 and the bond paper 220 at a temperature of 90° C. forone second. Referring now to FIG. 2B, the heated bars 225 are thenremoved (arrows 235) and a laminate 240 is formed. The laminate 240 iscooled for one minute. Next, the BPF 205 is peeled off from the bondpaper 220 by applying two opposing forces 245. Any suitable tensiletester unit such as a 5500R Model 1122 commercially available fromINSTRON may be used to conduct the peel strength experiment.

The BPFs of this disclosure may be converted to various end-usearticles. Examples of end use articles into which the BPFs of thisdisclosure may be formed include laminates (for packaging, printedpapers, etc.), laminate flooring compositions, polymeric foam substrate,decorative surfaces (e.g., crown molding, etc.), weatherable outdoormaterials, point-of-purchase signs and displays, housewares and consumergoods, cosmetics packaging, outdoor replacement materials, lids andcontainers (i.e., for deli, fruit, candies and cookies), appliances,utensils, and the like.

EXAMPLES

The disclosure having been generally described, the following examplesare given as particular embodiments of the disclosure and to demonstratethe practice and advantages thereof. It is understood that the examplesare given by way of illustration and are not intended to limit thespecification or the claims to follow in any manner.

Example 1

The strength of adhesion for a BPF comprising an mPP film layer and aBOPP film layer produced at 440° F. was investigated. A BPF sample,designated Sample 1, was prepared. The BOPP film used was a coronatreated BOPP film from OppFilm, Lima, Peru. The mPP used was EOD02-15,which is an mPP with an SIT of 105° C. available from TotalPetrochemicals USA, Inc. No tie layer was used between the mPP and BOPPfilm.

The sample was produced by extrusion coating an mPP layer onto the BOPPfilm using a laboratory extruder as described previously with referenceto FIG. 1. The details of processing parameters including temperatures,pressures, die gap, and screw speed for all samples are tabulated inTable 6. The thickness of the mPP film was adjusted by adjusting theline speed resulting in an mPP layer that was approximately 1 mil (25μm) thick. The final BPF thickness was 2.0 mil (50 μm).

TABLE 6 Parameter Zone 1 temperature 370° F. Zone 2 temperature 400° F.Zone 3 temperature 415° F. Zone 4 temperature 440° F. Clamp ringtemperature 440° F. Adaptor temperature 440° F. Feedblock temperature440° F. Die temperature 440° F. Melt temperature 408° F. Melt pressure290 psig Die gap 10 mil Screw speed 8 rpm Nip roll pressure 50 psigChilled roll pressure 40 psig Film speed 20 ft/min

The adhesion strength of Sample 1 was determined by measuring the 180°peel force as discussed previously herein with reference to FIG. 2. Theexperiment was repeated six times. FIG. 3 shows the 180° peel force as afunction of extension.

Example 2

The strength of adhesion between an mPP layer and a BOPP layer of a BPFproduced at 500° F. was investigated. A bi-layer film sample, designatedSample 2, was prepared. The component materials and method of producingthe bilayer film were described in Example 1. The details of processingparameters including temperatures, pressures, die gap, and screw speedfor all samples are tabulated in Table 7. The thickness of the mPP filmwas adjusted by adjusting the line speed resulting in an mPP layer thatwas approximately 1 mil (25 μm) thick. The final BPF thickness was 2mil.

TABLE 7 Parameter Samples 7-12 Zone 1 temperature 370° F. Zone 2temperature 400° F. Zone 3 temperature 415° F. Zone 4 temperature 450°F. Clamp ring temperature 500° F. Adaptor temperature 510° F. Feedblocktemperature 510° F. Die temperature 510° F. Melt temperature 427° F.Melt pressure 350 psig Die gap 10 mil Screw speed 12 rpm Nip rollpressure 50 psig Chilled roll pressure 40 psig Film speed 20 ft/min

The adhesive strength of Sample 2 was determined by measuring the 180°peel force and the experiment was repeated six times. FIG. 4 shows the180° peel force as a function of extension.

The results demonstrated that the 180° peel forces were higher forSample 2 when compared to Sample 1 from Example 1. The results suggestthat EOD02-15 has a greater adhesive strength when coated at 500° F.instead of 440° F. as shown in Example 1.

Example 3

The strength of adhesion between an mPP and a BOPP of a BPF produced at440° F. was investigated using an mPP having a lower SIT. A bi-layerfilm sample, designated Sample 3, was prepared. The BOPP used was thatdescribed in Example 1 and the mPP was EOD07-21, which is an mPP with aSIT of 98° C. available from Total Petrochemicals USA, Inc. The detailsof processing parameters including temperatures, pressures, die gap, andscrew speed for Sample 3 are tabulated in Table 6. The thickness of themPP film was adjusted by adjusting the line speed so resulting in an mPPlayer that was approximately 1 mil (25 μm) thick. The final BPFthickness was 2.0 mil.

The adhesive strength of Sample 3 was determined by measuring the 180°peel force and the experiment was repeated five times. FIG. 5 shows the180° peel force as a function of extension. The results demonstratedthat the 180° peel forces were not higher for Sample 3 when compared toSample 1 from Example 1.

Example 4

A bi-layer film sample, designated Sample 4, was prepared. The BOPP andthe mPP used were similar to those used Example 3. The bilayer films(approximately lmil thick) were produced using procedures similar tothose described in Example 1. The details of processing parametersincluding temperatures, pressures, die gap, and screw speed were similarto Example 2 which are tabulated in Table 7.

Sample 4 was tested for the adhesion by measuring the 180° peel forceand the experiment was repeated 7 times. FIG. 6 shows the 180° peelforce as a function of extension. The results demonstrate that the 180°peel forces were lower for Sample 4 when compared to Sample 2 fromExample 2. The results were surprising since EOD07-21 has a lower SITthan EOD02-15. In addition, the increase in peel force trend observed byincreasing the processing temperature from 440° F. to 500° F. as shownin Examples 1 and 2 was not observed for Examples 3 and 4.

Example 5

The haze and gloss of Samples 1-4 from Examples 1-4 were determined. Theresults are tabulated in Table 8.

TABLE 8 Sample 1 Sample 2 Sample 3 Sample 4 Haze % 6.3 6 5.4 1.8 Hazestd. dev 0.18 0.16 0.19 0.95 Gloss 45° 79 64 68.8 83.3 Gloss 45° std.dev 4.4 5.6 6.4 3.2

The results demonstrated that significantly clear and glossy filmstructures can be produced with either EOD02-15 or EOD07-21.

Example 6

The average 180° peel force for Samples 1-4 from Examples 1-4 weredetermined. The results are shown in FIG. 7, which is a plot of average180° peel force as a function of extension. Referring to FIG. 7,EOD02-15 extrusion coated at 500° F. (Sample 2) shows a higher average180° peel force than the other samples, which suggests that EOD02-15extrusion coated at 500° F. had higher adhesion strength to BOPP films.

Example 7

Films comprising a BOPP layer and an EVA coating with differing tielayers were prepared and the adhesion of the BOPP and EVA compared. Fourfilms, designated Samples 5-8, were prepared using EOD05-07 as the baseresin. EOD 05-07 is a polypropylene resin commercially available fromTotal Petrochemicals USA, Inc. Sample 5 included the BOPP film and a tielayer having a corona treated Basell 7432 resin. Basell 7432 is anethylene-butylene-propylene terpolymer layer commercially available fromBasell Service Co, The Netherlands. Sample 6 had the BOPP film and a tielayer including a corona treated HLDPE FH35 SC35 resin. HLDPE FH35 SC35is a medium density polyethylene layer commercially available fromBraskem, Brazil. Sample 7 had a corona treated BOPP film without a tielayer. Sample 8 had a BOPP film and a tie layer including a coronatreated Basell 7416. Basell 7416 is an ethylene propylene copolymerlayer, commercially available from Basell Service Co, The Netherlands.The thickness of the BOPP films was 0.0010 in. The surface tension ofthe corona-treated side of all samples was measured using AccuDyne TestInk and the results are tabulated in Table 9.

TABLE 9 Sample Surface Tension (dyne/cm) 5 ~57 6 >69 7 >69 8 >69

Next, Samples 5-8 were extrusion coated with a 1 mil (−25 μm) thick EVAlayer to form Samples 9-12 using a similar procedure describedpreviously. The EVA was ELVAX 460 resin, which is a commerciallyavailable 18% vinyl acetate EVA resin from DuPont, North America. Thedetails of processing parameters including temperatures, pressures, diegap, and screw speed for all samples are tabulated in Table 10.

TABLE 10 Parameter Samples 7-12 Zone 1 temperature 370° F. Zone 2temperature 400° F. Zone 3 temperature 415° F. Zone 4 temperature 450°F. Clamp ring temperature 470° F. Adaptor temperature 470° F. Feedblocktemperature 470° F. Die temperature 470° F. Melt temperature 428° F.Melt pressure ~1900 psig Die gap 10 mil Screw speed 23 rpm Nip rollpressure (L/R) 50/60 psig Take-off top roll temperature 55° F.

Paper separators were manually attached to the BOPP film at regularintervals upstream of the extrusion die during the coating process toprovide separation points between the EVA coating and the BOPP film. The180° peel tests were conducted on Samples 9-12 and were repeated between5-8 times. The results for Samples 9-12 are shown in FIGS. 8-11respectively. FIG. 12 shows the average 180° peel force as a function ofextension for Samples 9-12.

The results demonstrate that EVA adheres strongly to the BOPP filmcomprising a corona treated ethylene propylene copolymer tie layer(Sample 12) and poorly to the corona treated BOPP homopolymer (Sample11). The results further demonstrate that a mPP of the type describedherein (e.g., EOD02-15) exhibits increased adhesion to a corona treatedBOPP surface than an 18% EVA material. The clarity and low melting pointof an MPP of the type described herein could prove highly beneficial forcertain lamination applications. Furthermore, the simplicity of abi-layer sealable material, when compare to a tri-layer EVA/RCP/BOPPmaterial, may also beneficially impact the costs associated with theproduction of laminates.

While various embodiments have been shown and described, modificationsthereof can be made by one skilled in the art without departing from thespirit and teachings of the disclosure. The embodiments described hereinare exemplary only, and are not intended to be limiting. Many variationsand modifications of the subject matter disclosed herein are possibleand are within the scope of the disclosure. Where numerical ranges orlimitations are expressly stated, such express ranges or limitationsshould be understood to include iterative ranges or limitations of likemagnitude falling within the expressly stated ranges or limitations(e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numericalrange with a lower limit, R_(L), and an upper limit, R_(U), isdisclosed, any number falling within the range is specificallydisclosed. In particular, the following numbers within the range arespecifically disclosed: R=R_(L)+k*(R_(U)−R_(L)), wherein k is a variableranging from 1 percent to 100 percent with a 1 percent increment, i.e.,k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97percent, 98 percent, 99 percent, or 100 percent. Moreover, any numericalrange defined by two R numbers as defined in the above is alsospecifically disclosed. Use of the term “optionally” with respect to anyelement of a claim is intended to mean that the subject element isrequired, or alternatively, is not required. Both alternatives areintended to be within the scope of the claim. Use of broader terms suchas comprises, includes, having, etc. should be understood to providesupport for narrower terms such as consisting of, consisting essentiallyof, comprised substantially of, etc.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present disclosure. Thus, the claims are a further description andare an addition to the embodiments of the present disclosure. Thediscussion of a reference is not an admission that it is prior art tothe present disclosure, especially any reference that may have apublication date after the priority date of this application. Thedisclosures of all patents, patent applications, and publications citedherein are hereby incorporated by reference, to the extent that theyprovide exemplary, procedural, or other details supplementary to thoseset forth herein.

1. A method comprising: forming a bilayer polymer film comprising anoriented polypropylene film and a metallocene-catalyzed polypropylenefilm wherein the metallocene-catalyzed polypropylene film has a sealinitiation temperature of from 80° C. to 130° C.
 2. The method of claim1 wherein the metallocene-catalyzed polypropylene film has a thicknessof from 0.1 mil to 20 mil.
 3. The method of claim 1 wherein the orientedpolypropylene film comprises uniaxially oriented polypropylene film,biaxially oriented polypropylene film, or combinations thereof.
 4. Themethod of claim 1 wherein the oriented polypropylene film is coronatreated.
 5. The method of claim 1 wherein the oriented polypropylenefilm has a thickness of from 0.1 mil to 20 mil.
 6. The method of claim 1wherein the bilayer polymer film has an adhesive strength of from 0.1lb_(f) to 10 lb_(f).
 7. The method of claim 1 wherein the bilayerpolymer film has a gloss 45° of from 60 to
 99. 8. The method of claim 1wherein the bilayer polymer film has a haze percentage of from 0.5% to10%.
 9. The method of claim 1 wherein the bilayer polymer film has athickness of from 0.2 mil to 20 mil.
 10. The method of claim 1 whereinthe forming of the bilayer polymer film occurs at a temperature of from420° F. to 530° F.
 11. The method of claim 1 wherein the forming of thebilayer polymer film occurs by extrusion coating themetallocene-catalyzed polypropylene film onto the biaxially orientedpolypropylene film.
 12. The method of claim 1 further comprising:thermolaminating the bilayer polymer film with a substrate to form alaminate wherein the metallocene-catalyzed polypropylene film isdisposed between the biaxially oriented polypropylene film and thesubstrate.
 13. The method of claim 12 wherein the substrate comprisespaper, plastic, metal, wood, fabric, glass or combinations thereof. 14.The method of claim 12 wherein the laminate is substantially free ofethylene-vinyl-acetate.
 15. The method of claim 1 wherein the orientedpolypropylene film is subjected to a surface modification process. 16.An article produced by the method of claim
 1. 17. A laminate comprising:a biaxially oriented polypropylene film, a metallocene-catalyzedpolypropylene film, and a substrate, wherein the metallocene-catalyzedpolypropylene film is disposed between the biaxially orientedpolypropylene film and the substrate.
 18. The laminate of claim 17wherein the metallocene-catalyzed polypropylene film has a sealinitiation temperature of from 80° C. to 130° C.
 19. The laminate ofclaim 17 wherein the laminate is substantially free ofethylene-vinyl-acetate.
 20. The method of claim 17 wherein the biaxiallyoriented polypropylene film is subjected to a surface modificationprocess.